1. Field of the Invention
The present invention relates to a recording/reproducing device and a laser driving pulse adjusting method for optical recording media, for example, recording optical discs.
2. Description of the Related Art
In the recording technology for optical discs, a recording parameter constituting a recording waveform formed by a laser is generally referred to as a write strategy, and a laser is driven to be emitted based on the write strategy so that information is recorded. In the recording of information on an optical disc, adjusting a parameter of the write strategy in order to attain high recording quality is called write strategy adjustment.
The write strategy adjustment is generally performed by making corrections to a reference strategy. The reference strategy is a basic write strategy, which is used as a predetermined reference, and a specific numerical value of the reference strategy can be set by a media manufacturer (recorded in advance on a medium) or stored in advance in a drive.
Here, generally, the write strategy adjustment can be performed for each optical disc to be loaded in a drive. That is, the write strategy is known to be closely related to the material and thickness of the recording film of an optical disc, the configuration of the grooves, and the like, and it is thus necessary that the write strategy be optimized for each optical disc to be used.
In addition, the write strategy adjustment is necessary for reducing variations in drives.
In this case, there are the following reasons that each of the drives performs the write strategy adjustment.
That is, in the market, many types of optical discs that are difficult to be handled by drive manufacturers are distributed, and so much research effort is necessary for preparing appropriate write strategies in advance for all optical discs distributed in the market. This is time-consuming and also raises the cost of drives. Additionally, measures such as firmware updates for drives are necessary in order to respond to media distributed after the drives are shipped, which is also time-consuming.
Due to the reasons described above, it is necessary that the write strategy adjustment is performed by drives during recording.
An example of a specific technique of the write strategy adjustment is disclosed in, for example, Japanese Unexamined Patent Application Publication No. 2000-200418.
Japanese Unexamined Patent Application Publication No. 2000-200418 described “Standard recording pulse conditions specifying recording pulse positions for plural possible mark length and space length combinations are read from a writable optical disk. These standard recording pulse conditions are used for test writing. The standard recording pulse conditions are changed uniformly or individually, and a best recording pulse condition is obtained, thereby reducing jitter”.
Disclosed is the simplest technique that the write strategy is changed several times based on the reference strategy, and subjected to test writings. Then, signal quality evaluation values for the test writings are acquired, and a write strategy with the most excellent signal quality is used in actual recording.
By employing such a technique, variations of individual optical discs and drives are reduced, thereby adjusting to an optimized write strategy.
However, since the amount and orientation of variation of the optimized write strategy from the reference strategy vary depending on the combination of optical disc drives, in order to realize strategy adjustment with high accuracy in the technique disclosed in Japanese Unexamined Patent Application Publication No. 2000-200418, test writing is supposed to be performed which is assigned with adjustment values of the write strategy in a relatively extensive range. In other words, from this point, the technique disclosed in Japanese Unexamined Patent Application Publication No. 2000-200418 tends to have a large amount of test writing to be performed for the strategy adjustment, and there is a problem that a long adjustment time is necessary accordingly.
It is effective to use calculation by linear approximation to achieve reduction in the adjustment time, and for example, Japanese Unexamined Patent Application Publication Nos. 2008-84376 and 2007-521183 disclose an example of the specific technique.
Japanese Unexamined Patent Application Publication No. 2008-84376 discloses “When setting of two or more levels of power of laser light, a recording operation is performed for adjustment in an optical recording medium in different conditions of adjustment settings for a recording pulse, signals recorded by the recording operation are read to calculate a quality evaluation value, which is an index of recording signal quality, based on the setting conditions of the recording pulse. Thereby, quality evaluation values can be obtained for each of the setting conditions under each power setting, and an adjustment setting of the recording pulse is determined based on the quality evaluation values for each of the setting conditions of power. Accordingly, it is thus possible to determine the write strategy that can improve the total recording quality under the condition that a plurality of levels of recording power is set”.
In addition, Japanese Unexamined Patent Application Publication No. 2007-521183 discloses “By using each of three recording pulse conditions, particular recording patterns are continuously recorded onto an optical disc for test and the recording patterns are continuously reproduced. An edge shift amount of a mark corresponding to each of the three recording pulse conditions is measured from each reproduction signal, and from the measured value, a correction value of the recording pulse condition is calculated by linear approximation”.
In both of the techniques, test writing is performed for a plurality of write strategy and each of the signal evaluation values is obtained. Then, calculation is performed based on the result by using an arithmetic expression by a predetermined linear approximation, and the write strategy is adjusted.
Here, with reference to FIGS. 16A, 16B, and 17, a specific example of the flow of a series of adjustment processes including laser recording power adjustment when write strategy by such calculation is to be elicited will be explained.
FIGS. 16A and 16B show an example of the content (position) and arrangement order of each recoding on an optical disc in an adjustment operation, and FIG. 17 shows an example of the order of a process to be performed in order to realize an adjustment operation in such a case.
A writable optical disc medium, for example, Digital Versatile Disc (DVD)-R, DVD+R, DVD-RW, DVD+RW, Blu-ray Disc (BD: registered trademark)-R, or BD-RE, is provided with areas to be subjected to adjustment such as laser power or write strategy (adjustment area, test area) in innermost circumferential part and outermost circumferential part thereon. In the drawing, a case where adjustment using a test area in the outermost circumferential side is performed is exemplified.
In this case, each medium as described above is regulated such that the test area is used from the side of higher address numbers. A position A shown in FIG. 16A corresponds to a position A shown in FIG. 16B, and in the same manner, a position B shown in FIG. 16A corresponds to a position B shown in FIG. 16B.
In addition, in FIG. 16A, the arrow indicates a direction of writing and reading.
Moreover, on each medium as described above, a test area in the outermost circumferential part has about 5 clusters (a cluster is a unit of error correction) for one cycle.
In the example shown in FIGS. 16A, 16B, and 17, prior to an adjustment operation of the write strategy, adjustment operation of laser recording power, as so-called Optimum Power Control (OPC), is performed. Specifically, recording for recording power adjustment (Step S1001 in FIG. 17) as the recording power adjustment recording <1> shown in FIGS. 16A and 16B, acquisition of the evaluation value of the recording spot for <1> (S1002), and recording power adjustment based on the evaluation value (S1003) are performed.
As described above, since the case is regulated such that the test area is used from the side of higher address numbers, the recording power adjustment recording <1> is performed such that a cluster with the highest address number (a cluster in the outermost circumference in this case) within an unrecorded area is used in the test area. In this case, since the recording power adjustment recording <1> has a recording length of one cluster as shown in FIG. 16A, the recording power adjustment recording <1> is performed for the cluster with the highest address number.
Then, trial writing and acquisition of evaluation values are performed for strategy calculation. Specifically, as the strategy calculation and recording for reproduction pull-in (S1004), recording from reproduction pull-in recording <5> to strategy calculation recording <4> to <2> in FIGS. 16A and 16B is performed, and then, evaluation values of each recording spot of strategy calculation recording <4> to <2> are acquired (S1005).
Here, the reproduction pull-in recording <5> is a process for performing signal recording for a pull-in process necessary for reproducing data, such as pull-in of, Phase Locked Loop (PLL), Auto Gain Control (AGC), or the like. It is needless to say that the reproduction pull-in recording <5> is used as a pull-in area when the recording spots of the strategy calculation recording <4> to <2> are reproduced in the acquisition of evaluation values.
In addition, the strategy calculation recording <4> to <2> is a process for performing signal recording by changing each of the write strategies several times.
After the evaluation values are acquired for each of the strategy calculation recordings <4> to <2>, an optimized write strategy is calculated based on the evaluation values (S1006). In other words, an optimized write strategy is calculated based on a predetermined arithmetic expression (an arithmetic expression by linear approximation) and the evaluation values.
Then, a write strategy calculated as such is set (S1007).